1. Field of the Invention
The present invention relates to improvements in self-propelled working machines, such as snow removing machines and cultivating machines.
2. Background Information
In recent years, there have been developed self-propelled working machines which are controllable by a human operator manipulating an operating handle unit while walking, with a view to reducing human labor necessary for intended work, such as snow removing work or agricultural work. Such working machines are known, for example, from Japanese Patent Publication No. SHO-51-30378 (hereinafter “Patent Document 1”), Japanese Patent Publication No. SHO-53-5210 (hereinafter “Patent Document 2”) and Japanese Patent Application Laid-open Publication No. 2001-271317 (hereinafter “Patent Document 3”).
FIG. 12 is a side view showing one side of an auger-type snow removing machine disclosed in Patent Document 1 (Japanese Patent Publication No. SHO-51-30378). The disclosed snow removing machine 300 includes left and right crawler belts (only the left crawler belt is shown) 301 each supported on a corresponding traveling-component supporting frame 302, a main frame 303 mounted above the traveling-component supporting frames 302 for vertical pivotal movement about a pivot axis 309, an engine 304 mounted on an upper surface portion of the main frame 303, and a snow removing working section 305 secured to a front portion of the main frame 303. The snow removing machine 300 also includes a jack 306 which can cause not only the arm frame 303 but also the engine 304 and snow removing working section 305 to pivot vertically. The engine 304 drives the snow removing working section 305, including an auger 307 and blower 308, to perform snow removing work.
FIG. 13 is a side view of an auger-type snow removing machine disclosed in Patent Document 3 (Japanese Patent Application Laid-Open Publication No. 2001-271317). In the disclosed snow removing machine 400, power from a horizontal engine 402 having a crankshaft 401 extending horizontally forward is transmitted to a snow removing working section 405 via a snow-removing power transmission mechanism 403 and transmission shaft 404, and power from left and right electric motors 406 is transmitted to left and right crawler belts 409 via driving axles 407 and driving wheels 408. More specifically, in the snow removing machine 400, the motors 406 and driving wheels 408 are mounted on rear portions of corresponding traveling-component supporting frames 411, while idle wheels 412 are mounted on front portions of the corresponding traveling-component supporting frames 411. The crawler belts 409 are passed around the driving wheels 408 and idle wheels 412, and a vehicle body frame or main frame 413 is provided above the traveling-component supporting frames 411 for vertical pivotal movement about a pivot axis 417. The horizontal engine 402 and snow-removing power transmission mechanism 403 are mounted on an upper surface portion of the main frame 413, and the snow removing working section 405 is attached to a front portion of the main frame 413. The snow removing machine 400 also includes a frame elevator mechanism 414 which can cause the engine 402, snow-removing power transmission mechanism 403 and snow removing working section 405 to pivot vertically together with the main frame 413. The engine 402 drives the snow removing working section 405, including an auger 415 and blower 416, to perform snow removing work.
As set for the above, the engine 304 and working section 305 in the snow removing machine 300 of FIG. 12 are attached to the main frame 303, and the engine 402, snow-removing power transmission mechanism 403 and snow removing mechanism 405 in the snow removing machine 400 of FIG. 13 are also attached to the main frame 413. Thus, the main frame in each of the above-discussed conventional snow removing machines 300 and 400 must have a large size, relatively complicated shape and high rigidity. Thus, the conventional snow removing machines 300 and 400 each tend to have a great overall size and weight as well as a large number of component parts. Similar inconveniences would be presented by the conventional machine disclosed in Patent Document 2.
Further, FIG. 14 is a side view of an auger-type snow removing machine disclosed in Patent Document 4 (Japanese Patent Application Laid-Open Publication No. SHO-63-513). In the disclosed snow removing machine 500, power from a horizontal engine 502 having a crankshaft 501 extending horizontally forward is transmitted to a snow removing working section 506 via a snow-removing power transmission mechanism 503 accommodated in a transmission case 503 and a transmission shaft 504, and the power from the horizontal engine 502 is also transmitted to left and right crawler belts (only the left crawler belt is shown) 509 via a driving axle 507 and driving wheels 508. More specifically, in the snow removing machine 500, the horizontal engine 502 is mounted on traveling-component supporting frames 512 supporting thereon idle wheels 511 of the left and right crawler belts 509, the transmission case 503 is connected to a front end portion of the engine 502, and the snow removing working section 506 is attached to a front end portion of the transmission case 503. Further, the driving axle 507 is secured to a lower portion of the transmission case 503, and the left and right driving wheels 508 are mounted on the driving axle 507. The snow removing working section 506, which includes an auger 521 and blower 522, is driven by the engine 502 to perform snow removing work. In this machine 500, the snow removing working section 506 is not constructed to pivot vertically. Generally, an enhanced snow removing efficiency and finish quality may be provided by making arrangements for allowing the lower end portion of the snow removing working section 506 to readily bite into the snow surface. For that purpose, it is preferable to set the center of gravity of the snow removing machine 500 at a position closer to the front end of the machine 500. However, if the center of gravity of the snow removing machine 500 is too close to the front end, traveling performance of the crawler belts 509 on the snow surface would be adversely influenced. Thus, it is more preferable to set the center of gravity of the snow removing machine 500 at a position close to the front end of the machine 500 and near the driving axle 507.
However, because the snow removing machine 500 includes the snow removing working section 506 in a front portion thereof, the horizontal engine 502 having its crankshaft 501 extending horizontally forward has to be provided in a rear portion of the machine 500. Thus, the heavy engine 502 is located immediately above the idle wheels 511 that are located remotely from and rearward of the driving wheels 508 with a great distance formed from the engine 502 to the snow removing working section 506, which would thereby increase the overall size of the snow removing machine 500. Due to the great length, the snow removing machine 500 would present a poor turning capability. Further, because the heavy engine 502 is positioned near the rear end of the machine 500, some consideration has to be made to set the center of gravity of the snow removing machine 500 at an optimal position.
One possible approach for avoiding the inconveniences is to replace the horizontal engine 502 with a vertical engine having a vertically-extending crankshaft. But, merely employing such a vertical engine would considerably complicate the construction of the snow removing machine 500. Similar inconveniences would occur in the conventional machine 400 disclosed in Patent Document 3.